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Welding supercharger cases together

04-18-2008, 02:54 AM

I've been asked to weld two 6V71 supercharger cases together (end to end) to efectively get a 12V71. The owner of them says he can couple the rotors and I only have to join the cases. My main concern would be warpage causing misalignment, which would pretty much stuff the blowers. I know I can bolt them to heavy plate while they're being welded but still have concerns. Has anyone ever done this, or seen or heard of it being done sucessfully? Do you think dowelling and bolting the cases together would be better?

dont know if this helps or not. but we weld snowmobile crankcases together. you can take a 2 cylinder engine. cut a half a cylinder off of each engine and weld them together to get a big 3 cylinder. use a steel plate on the top and bottom. tack around and then jump around and weld. what they do is weld a bead on this side then on the other side and get it all welded.

dont know how much help that is but never have to many problems with cranks.

also if you do a true job once he has it bolted down to the engine it should help eliminate twist.

Comment

Like mentioned before, alignment would be very critical here. I would discuss this thorougly with the person you are doing the work for and make sure that they think it will work before you start. You may also want to get some sort of signed document saying you are not liable for parts costs if things don't work out. Unfortuanetely in todays world one must always look out for himself.

If you do go for it, and things work out, make sure you post lots of pictures.

Comment

I would say it can be done.. but best to plan to have it re machined after you are done welding, both the flat surfaces and the bores the rotors fit in. Then oversize rotors may be needed.

For Detroit Diesels a scored blower housing (eats to much dirt) is scraped and a new one is found, they don't often crack, if they do there is something else going on.

If he throws enough money at it, it could work, but I doubt it is as simple as he thinks. Not sure how he plans to attach the rotors either, but they need to be just right to, as clearance around the rotors and case is less than 0.010", nothing touches in a Detroit blower, just the shafts in the bearings or end housings.

I bet the long rotors flex to much in the middle and hit the case.
Detroit did make a 12V71, but it used two blowers, but just one crankcase. If it had been a good idea to use one long blower I bet they would have done it to start with.

Comment

Thanks for the feedback guys. Surprisingly, I don't think he uses mind altering substances except a bit of alcohol. I did not think of the flex of doubling the length of the rotors, but it's surely another possible problem. Set up side by side or in a V configuration, or one on top of the other are probably all workable options, but he does want to run three four barrels.

Comment

Using a tunnel ram on a Ford is fairly common to clear the distributor.

With the availability of 12-71 and 14-71 cases new or used, why would anyone go to the trouble of welding two together? You could buy a used up case from a drag racer and still have plenty of umph for a street car.

Comment

It's my car he's asking about. Why weld two 6V71's together? Because it would make a really big blower. the 8, 10, 12 71 aftermarket blowers are 1 inch longer than a 671 per 2 number add, ie an 871 is long inch longer than a six and a 1071 is two inchs longer. A 671 is just under 15 inchs long, a 6V71 is just under 12 inchs long. Therefore 2 x 6v71 would be almost 24 inchs long, ie about the same as a 2471. So as well as being massive, It adds to the freak value of the car. Car will be running 3 x 660 centre squirters, same reason, cause I can and cause I'm a freak.

Comment

It's my car he's asking about. Why weld two 6V71's together? Because it would make a really big blower. the 8, 10, 12 71 aftermarket blowers are 1 inch longer than a 671 per 2 number add, ie an 871 is long inch longer than a six and a 1071 is two inchs longer. A 671 is just under 15 inchs long, a 6V71 is just under 12 inchs long. Therefore 2 x 6v71 would be almost 24 inchs long, ie about the same as a 2471. So as well as being massive, It adds to the freak value of the car. Car will be running 3 x 660 centre squirters, same reason, cause I can and cause I'm a freak.

Freak, yes. Typist no. Reading that was like talking to my 10 year old nephew!
I get what your saying, it would be really wild. If your going for show, then great. If your going racing i think is probably a poorly conceived waste. I'm not sure why, but i don't think it will perform very well. May well make too much boost or heat.

Comment

Too much boost or heat? Can't see an issue with either. Boost is set by pulley raio . Since to combined size of the blowers make 654ci per revolution then its just a matter of underdriving to achieve the desired boost. As for heat, since the blower will be spinning slow due to the underdriven nature, then heat should be less of an issue than using a normal sized blower. I am considering putting the blowers back to back before welding and leaving a set of gears at each end of the blower to maintain them in the correct timing and stop then from untwisting due to the length. Any thoughts on this? I understand it an "out there" idea but that is part of the point. Hot Rodding isn't about building a mass producted vehicle but rather an individual piece of "automotive art." The car may see some strip time, but it is not a drag car. I will also only weld the blowers end for end if I am sure it will work, which is why I'm after peoples input. Otherwise I will stick with the 8V71 I already have. (The car will also be running multiple nitrous systems) Yes I am a Freak, but not a fool.